In late October, a coronal mass ejection (CME) — a violent explosion of subatomic particles erupting from the Sun at high speeds — blasted away from our star, impacting the Earth, and setting off aurorae seen as far south as Arkansas. It was cloudy here in Boulder, but from space, the view is always clear. NASA’s STEREO spacecraft are twin machines, one ahead of the Earth, one behind, both staring at the Sun 24/7. They are currently roughly 100° around the Earth’s orbit, so they are essentially seeing the Sun "from the side".

STEREO A, ahead of the Earth in its orbit, captured images of the Sun during October’s solar hissy fit, and got dramatic footage of the explosion:

Yegads. [Make sure you click the HD button to see this in all its glory.]

The Earth is off to the left, well off-screen, in this animation. The Sun is blocked by a circular mask, so fainter things can be seen (its disk is represented by the white circle). The big CME occurred early on October 22 and is followed by others.

The energy and raw power of this event is staggering: a billion tons of matter was hurled away from the Sun at several million kilometers per hour. This completely dwarfs into nothing all of humankind’s energy output, and is vastly greater than the explosive yield of all nuclear weapons at the height of the Cold War combined.

And during its active phase, the Sun tosses these things off like a gourmand barely stifles a belch.

The danger to Earth from CMEs is real, if rare. A powerful one can generate strong electric currents in conductors (like power lines) on the Earth’s surface, which can cause widespread blackouts. They can also damage satellites in orbits or be a radiation danger to astronauts. In general, though, our magnetic field protects us on the ground, preventing us from suffering any direct danger. And, as a bonus, we can get beautiful displays of aurorae out of them. While they’re a concern for us as an electricity-using and space-faring race, we can protect ourselves from their danger while simultaneously reveling in their power and majesty.

@1 DennyMo
That’s a loaded question there. What really matters is the angular size. Something which is farther away looks smaller. But looking at the Sun’s distance, the ratio of the solar diameter to the camera’s diameter is about 13. So the diameter which is seen at the Sun’s distance is ~18 million km.

Our Sun is in the top 5% of stars mass and luminosity~wise with the vast majority of stars being very much smaller (only Jupiter sized in some cases) and fainter red dwarfs which make up 70% of all stars – although we cannot see a single one without optical assistence! Another 15% of stars are slightly brighter and more massive K type orange dwarfs such as Epsilon Eridani, Epsilon Indi and 61 Cygni.

Another 10% of stars – and ever rising – are white dwarfs which cram about a Sun to a Sun-and-a-half’s worth of mass into a sphere ranging from about the size of Neptune down to less than the radius of Earth* and thus because of tehir tiny size are very much fainter with not a one visible to unaided human eyes.

In fact, G type yellow dwarfs stars ike our Sun make up only 4% of the total stellar population – and our Sun is a relatively hot and massive example of the class G2 being only a couple of steps (G0 & G1) below being a F-type Procyonese star. Spectral class A & F Sirian and Procyonese dwarfs make up 1% with all other higher mass and luminosity classes (W**, O, B plus the chemical classes R, N, S) comprising less than 1% of all stars.

Based on the vague quantities given, I approximate the energy involved at 100 quadrillion kW-hr. (“a billion tons of matter was hurled away from the Sun at several million kilometers per hour” –> 10^12 kg at n*10^9 m/hr –> 10^12 kg at ~10^6 m/s –> .5*10^24 J –> 1.4*10^17 kW-hr)